If you're a horse, how old is old?
BLM sells wild horses over 10-years-old "without limitation" ; they can be killed and sold for slaughter, just like young horses which haven't found families. from their website:

"In addition to placing wild
horses and burros into good homes through the adoption program, the BLM
directly sells animals that are more than 10 years old and those younger
that have been passed over for adoption at least three times."

After looking at the chart below, why do you think they choose that age?
Does your > 10 horse have any value?